As it is known boar semen, is more sensitive to the frozen-thawed process. The aim of this study was to improve the boar semen viability after the frozen – thawed process, this through the trehalose expositiotion in the cytoplasm of the boar sperm, by the formation of pores by the streptolysin–O (SLO) toxin. First, the cells were exposed to different concentrations of SLO (0.2 U/ml, 0.6 U/ml, 1U/ml and 5U /ml) to determinate the SLO concentration, that allows to maintain the sperm viability. The cells treated with 0.6 U/ml concentration of SLO showed the best membrane integrity percent (57.44% ± 2.26). Besides, the percentage of living sperm with intact acrosome, was higher in the cells treated with 0.6 U/ml SLO (63.72 % ± 1.75); therefore this SLO concentration was selected to iexpose to the trehalose the spermatic samples, wich would be cryopreserved. After the thawing, the treatment with 100 mM trehalose showed 40.61±3.08% the sperm with intact acrosome, while the control samples 13.61±3.08% (P˂0.05). However, there were not differences (P˃0.05) between 100 mM trehalose treatment (7.83±0.76) and the control (9.89±0.76).  In spite of the last result, the presences of trehalose on of the cryopreserved boar sperm, allowed to conserve a higer percentage of alive sperm. The incubation with SLO and trehalose (100 mM) of the boar sperm, increased the acrosome integrity after to the frozen-thawed process and maintained the viability. But is necessary more studies for determines, the effects over fertility.